From time to time, offshore structures in the form of large offshore platforms are erected on the ocean floor for the purpose of drilling a large number of wells into the ocean floor in order to develop and oil or gas fields. In shallow water locations where small amounts of oil and gas have been found, the erection of a large platform could not be economically justified. Thus, at times, only a single well need be drilled down to the oil deposit. Alternatively, single wells are often drilled in extensions of known fields to develop small deposits. At other times, it is often desired to drill a single well and evaluate the field production for a year prior to going forward with further drilling of that area.
In shallow water of, say, 50 to 150 feet in depth, a single well would be drilled by driving a large-diameter drive pipe or well conductor into the ocean floor from a jack-up rig. The well conductor, which may be 48 inches in diameter, forms the outer tubular member of a well installation. A well is drilled through the well conductor in a manner well known to the art and then is closed at the top by a well head assembly of the type used in producing a well. A single well of this type is normally protected by fabricating onshore a well protector jacket which is normally square in cross-section and extends for a height equal to the distance between the ocean floor and the wellhead at the top of the well conductor, say, 50 to 75 feet above the water surface. Such a jacket is transported by barge or otherwise to the offshore location where a derrick barge is employed to lift the jacket above the wellhead and slip it down over the wellhead and well conductor to the ocean floor. Piles are then driven down through the corner legs of the jacket to anchor it to the ocean floor.